In a traditional telephone network, ringback media is typically an audible tone sequence presented during a call process to a caller. The ringback media may signal to the caller that the called party's phone is being alerted of an incoming call from the caller to the called party. Upon hearing ringback media, the caller may generally assume that the called party is receiving a corresponding, concurrent (or nearly concurrent) alert, such as an audible ringtone sequence. The ringback media usually continues until either the called party (or a call-handling function such as an answering machine) answers the call or the caller hangs up before the call is answered. The period within the call process during which ringback media is played is typically referred to as the ringback period.
The model for ringback media has evolved similarly in both circuit-switched telephony with out-of-band signaling and services (Signaling System 7 (SS7) and Advanced Intelligent Network (AIN), for example), and packet-based telephony, such as Voice over Internet Protocol (VoIP). Ringback media in these types of systems is typically stored as an audio data file on a network entity such as a ringback server, and played out to a caller's phone during the call process when the entity receives a signal, from a terminating switch for example, indicating that the called party's phone is being alerted.